Such cutting chisels are generally used on cutting rollers of ground processing machines, in particular road construction machines, mining machines or the like.
The cutting rollers of road milling machines, mining machines or the like are usually provided with chisel holder changing systems. In this instance, base portions of the chisel holder changing systems can be connected to the surface of a cutting roller pipe, in particular welded or screwed thereto. In this instance, the base portions are positioned relative to each other so that helical loading members are produced on the surface of the cutting roller. Chisel holders are connected to the base portions, wherein the chisel holders may be screwed, welded or otherwise retained with respect to the base portion, for example, clamped. In the simplest case, the chisel holders may also be directly connected to the surface of a cutting roller pipe. The chisel holders have a chisel receiving member. The chisels described above can be mounted therein so as to be able to be replaced. During use of the machine, the chisels strike with the chisel tips thereof the substrate which is intended to be removed and cut into it. In this instance, the ground material is broken up. The material which has been removed in this manner can be transported, for example, via the helical broaching and loading members toward the center of the cutting roller and conveyed out of the operating region of the cutting roller at that location by means of ejectors. The material can then be transported away using appropriate devices, for example, transport belts. The chisels are provided with chisel tips, which comprise hard material and which bring about the cutting engagement. They are consequently subjected to an abrasive attack and must therefore comprise a suitable hard material in order to achieve the longest possible service-life. From the prior art there are known chisels in which the chisel tip comprises hard metal. In order to be able to generate uniform wear at the periphery with such chisels, the chisels are generally rotatably arranged in chisel receiving members of the chisel holders.
There are also known chisels which are provided in the region of the chisel tips thereof with a “superhard material”. For example, the chisel tips have a coating of polycrystalline diamond or another material which has a hardness which is comparable with diamond. Such a chisel is known from US 2012/0080930 A1. Such chisel tips have an extraordinarily long service-life and exhibit hardly any wear during operational use. It is therefore not absolutely necessary to fix these chisels in a rotatable manner in the chisel holders. US 2012/0080930 A1 therefore proposes providing the chisel shaft of the chisel with a thread and clamping the chisel securely to the chisel holder by means of a nut. If after a specific operating time wear appears on the chisel, the nut can be released, the chisel can be rotated slightly and the nut can then be retightened.
The chisel is supported with a support portion of the chisel head on a correspondingly formed counter-face of the chisel holder. In this instance, the support portion is constructed in a frustoconical manner and tapers from the chisel head in the direction toward the chisel shaft. During the cutting engagement of the chisel, the cutting force which acts on the chisel varies not only with regard to the value thereof, but also with regard to the force direction. In this instance, it may be the case inter alia that stresses which act in an impact-like manner act on the chisel in the case of uneven surface quality. Those loading situations may result in the support face of the chisel or the corresponding counter-face of the chisel holder being deflected and then the thread connection between the chisel and the chisel holder becoming loose. The chisel can then break or become lost.